Digestion and Absorbtion

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Digestive Enzymes

- Digestive enzymes are used to break down biological molecules in the food.

- Enzymes are specific and can only break down substrates that have a complementary shape with their active site.

-Amylase is an enzyme that is used to convert starch into a smaller sugar maltose, using hydrolysis reaction.

- Amylase is produced by the salivary gland ( released inside the mouth ),also by pancreas which releases the enzymes in small intestine.

Glucose + Glucose = Maltose

Glucose + Fructose = Sucrose

Glucose + Galactose = Lactose  

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Lipids are broken down by Lipase

- Lipase break down lipids into monoglycerides and fatty acids. This involves the hydrolysis of the ester bonds. Lipase are made in pancreas and work in the small intestine.

- Bile salts are produced by the liver and cause the lipids to form small droplets (emulsify).

- Several small lipid droplets have a greater surface area than a single large l droplet.

- The greater the surface area, the easier it is for Lipase ( enzymes ) to ge to droplets and break them down.

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Endopeptidases and Exopeptidases

Proteins are broken down by different combination of proteases. They catalyse the conversion of proteins into amino acids via hydrolasation.


- Act to hydrolysis the bonds within a protein

- Trypsin and Chymotrypsin are two examples of this that are produces in pancreas and released into the small intestine.


- Act to hydrolyse to remove a single amino acid from the end of the protein.

- Dipeptideases is an example of it that works specifically on dipeptides. They are often located in the cell surface membrane of epithelial cells of small intestine.

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The products of the Digestion are absorbed through the ileum epithelium ( in the small intestine ) into the bloodstream.

--> Monosaccharides

      * Glucose ( as well as Galactose ) is absorbed by active transport of         sodium ions via cotransporter protein. 

      * Fructose is absorbed via facilitated diffusion.

--> Monoglycerdes and fatty acids

      * Micelles help to move them towards the epithelium

--> Amino acids

      *They absorbed the same way as the glucose via sodium ions.

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